Distortion resisting and energy absorbing device

ABSTRACT

An arrangement for containing the grinding wheel fragments and the kinetic energy released therewith in the event of a grinding wheel failure in a high speed precision grinding machine, including a grinding wheel guard having a lower portion thereof of substantially constant U-shaped horizontal cross section open at its lower end and provided adjacent to its lower end with Ushaped sets of reinforcing ribs extending internally thereof toward the grinding wheel enclosed thereby, and including a distortion resisting and energy absorbing assembly fixedly mounted adjacent to and spanning the open lower end of the grinding wheel guard.

United States Patent Hnilicka, Jr.

[ Apr. 25, 1972 [54] DISTORTION RESISTING AND ENERGY ABSORBIING DEVICE Milo P. Hnilicka, Jr., Concord, Mass.

[73] Assignee: Norton Company, Worcester, Mass.

[22 Filed: Sept. 21, 1970 [21] Appl. No.: 76.513

[72] Inventor:

[52] U.S. Cl ..51/269 [51) Int. Cl ...B24b 55/04 [581 Field of Search ..51/268, 269

[56] References Cited UNITED STATES PATENTS 3,129,537 4/1964 Backer ..51/269 3,247,623 4/1966 Anderson ....5 H269 3,564,780 2/1971 Grzymek et al ..51/269 3,571,983 3/1971 Stewart ..51/269 Primary Examiner-William R. Armstrong Attorney-Lewis M. Smith, Jr.

[ 5 7] ABSTRACT An arrangement for containing the grinding wheel fragments and the kinetic energy released therewith in the event of a grinding wheel failure in a high speed precision grinding machine, including a grinding wheel guard having a lower portion thereof of substantially constant U-shaped horizontal cross section open at its lower end and provided adjacent to its lower end with U-shaped sets of reinforcing ribs extending internally thereof toward the grinding wheel enclosed thereby, and including a distortion resisting and energy absorbing assembly fixedly mounted adjacent to and spanning the open lower end ofthe grinding wheel guard.

2 Claims, 3 Drawing Figures DISTORTION RESISTING AND ENERGY ABSORBING DEVICE BACKGROUND OF THE INVENTION As the speed at which grinding wheels are rotated is progressively increased, it becomes increasingly difficult to provide effective means for containing the wheel fragments and the kinetic energy released therewith in the event of a grinding wheel failure, especially on large precision grinding machines equipped with grinding wheels 3 or more feet in diameter and 6 inches or more in thickness.

U.S. Pat. No. 3,526,998, issued Sept. 8, 1970, describes a grinding wheel guard assembly substantially enlarged above the grinding wheel enclosed thereby and open along most of the lower half of the periphery of the grinding wheel, so that high energy wheel fragments trapped in the enlarged space above the grinding wheel may be deflected downwardly and rearwardly through the open lower periphery of the wheel guard into the adjacent hollow space within a typical hollow cast iron grinding machine base.

US. Pat. No. 3,452,489, issued July 1, 1969, discloses supplemental means for containing wheel fragments in the event of grinding wheel failure which comprises a shutter assembly supported on four bar linkages and operative automatically in the event of grinding wheel failure to close the opening in the wheel guard assembly through which workpieces are presented to the grinding wheel for grinding operations.

U.S. Pat. No. 3,129,538, issued Apr. 21, 1964, discloses supplemental means for absorbing the energy released in the event of grinding wheel failure which comprises a wheel guard restraining means including elements designed to absorb predetermined substantial quantities of energy by deformation under tension when a grinding wheel guard is subjected to peak load conditions at the instant of grinding wheel failure which tend to separate the grinding wheel guard and the wheel slide from the base of the grinding machine.

However, the grinding wheel guard configuration described and illustrated in U.S. Pat. No. 3,526,998, is not so well suited to grinding machines which do not include a hollow base providing a safely located large receptacle for the wheel fragments deflected through the open lower peripheral portion of the grinding wheel guard, and the current trend is to increased use of grinding machine bases fabricated from welded steel plates which bases necessarily include an upper surface comprising a continuous structural steel plate which bars the passage ofwheel fragments into the interior of the base.

SUMMARY OF THE INVENTION The present invention provides a grinding wheel guard assembly particularly suitable for use on high speed precision grinding machines including fabricated base assemblies of the type preferred to above and other types of base assemblies with a fully closed top structural surface adjacent to the open peripheral side of the wheel guard assembly, and arranged to function in cooperation with an adjacent energy absorbing assembly to contain wheel fragments released by a grinding wheel failure and to absorb the kinetic energy released by a grinding wheel failure without substantial damage to the grinding wheel guard assembly or to other components of the grinding machine protected thereby.

More specifically, the energy absorbing assembly prevents damage to the grinding machine base and the peripheral and side portions of the wheel guard assembly adjacent to the energy absorbing assembly are provided with sets of reinforcing ribs surrounding the adjacent portion of the grinding wheel to protect the grinding wheel guard assembly itself.

BRIEF DESCRIPTION OF THE DRAWING Referring now to the drawing wherein like reference numerals refer to like or corresponding parts,

FIG. 1 is a side elevation, partially broken away on line 1-1 of FIG. 2 and elsewhere, of the preferred embodiment of the grinding wheel guard assembly and the associated energy absorbing assembly,

FIG. 2 is an enlarged horizontal section on line 2-2 of FIG. 1 showing details of the reinforcing ribs, and

FIG. 3 is an end view of portions of an additional energy absorbing device.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, grinding machine base 11 supports a wheel slide base 12 fixedly secured thereto, and in turn supporting wheel slide 13 arranged for sliding movement back and forth along the upper surface of wheel slide base 12, for example upon spaced flat and V-shaped ways, not shown, in the manner well-known in the art. A wheel spindle assembly 14 rotatable supported in the wheel slide 13 and rotated by a wheel drive motor, not shown, supports a grinding wheel 15 secured thereto by suitable mounting flanges and a retaining nut 16 for reciprocation with the wheel slide 13 and thereby for movement into and out of operative engagement with a workpiece 17 rotatably supported by headstock and footstock assemblies or other suitable workpiece supporting means, not shown, mounted upon the base 11.

The grinding wheel guard assembly generally designated by the reference numeral 20 encloses a predetermined portion of the periphery of the grinding wheel 15 within a combination of interconnected structural elements including a fixed peripheral portion 21, an adjustable hood 22 connected by pivotal connection 23 to upstanding flanges 24 attached by welding or otherwise to fixed peripheral portion 21, and a movable shutter 25 connected to opposite side portions of the hood 22 by two pairs of links 26 and pivot assemblies 27, all together forming the periphery of a substantially enlarged space above the grinding wheel 15 as and for the purpose described in U.S. Pat. No. 3,526,998.

The hood 22 is retained in its properly adjusted position with the lower lip of shutter 25 closely adjacent to the peripheral surface of the grinding wheel 15 by tightening a pair of bolts 28, and the shutter 25 is retained in its usual retracted position within the hood 22 by either one of the retaining screws 29, for automatic release, in the event of grinding wheel failure, in the manner described in U.S. Pat. No. 3,452,489.

The grinding wheel guard assembly 20 also includes spaced side portions 31 on opposite sides of the grinding wheel 15 connected along their edges to the adjoining respective opposite edges of the fixed peripheral portion 21. The rearmost side portion 31, as seen in FIG. 1, may be welded to the fixed peripheral portion 21, but to facilitate changing the grinding wheel, the foremost side portion 31, as seen in FIG. 1, may include flanges 32 removably secured to the fixed peripheral portion 21 by a series of attachment screws 33.

Housing 39 provides additional space within the grinding wheel guard assembly to accomodate a suitable wheel truing tool assembly and its periodic traversing movement across the periphery of the grinding wheel.

The grinding wheel guard assembly 20 shown in FIG. 1 is provided with an energy absorbing device comprising an upper block 41 secured to one side portion 31 by attachment screws and supporting a lower block 42 attached thereto by one or more tension bolts 48 designed to dissipate a predetermined amount of energy by elongation before they break.

The lower block 42 has a channel 43 along one side interfitted slidably with an elongated rib 44 projecting from one side of a base mounted bar 45 shown fastened to wheel slide base 12 by attachment screws 46, so that energy released when a grinding wheel breaks which tends to lift the grinding wheel guard assembly and the wheel slide to which it is attached off of the wheel slide base will be dissipated by elongation of tension bolts 48 as described in U.S. Pat. No. 3,129,538.

Noting the grinding wheel 15 is rotated clockwise, as seen in FIG. 1, wheel fragments released from the front and lower portions of a fractured grinding wheel are thrown with great force against the lower rear portion of the grinding wheel guard assembly 20, and wheel fragments released from the rear and upper portions of the fractured grinding wheel, initially collected in the enlarged space within the grinding wheel guard assembly above the grinding wheel, are also deflected by the hood 22 and the shutter 25 downwardly and rearwardly toward the lower rear portion of the grinding wheel guard assembly.

Consequently, this portion of the grinding wheel guard assembly is protected and reinforced by a series of spaced parallel U-shaped sets of reinforcing ribs 51 and 52 fixedly secured to the inner surfaces of the fixed peripheral portion and the respective side portions of the grinding wheel guard assembly, preferred to be by welding. The elongated ribs 51 attached to the foremost side portion 31, as seen in FIG. 1, are of such size and shape as to extend closely adjacent to one side surface of the grinding wheel 15, and the L-shaped ribs 52 attached to the rearmost side portion 31, as seen in FIG. 1, and to the fixed peripheral portion are positioned and of such size and shape as to extend closely adjacent to the other side surface of the grinding wheel and to its full size peripheral surface, respectively.

These sets of reinforcing ribs also serve to entrap small wheel fragments and collectively as a breaker assembly to engage and break up larger wheel fragments, thereby reducing the risk of damaging the portion of a wheel truing device, not shown, extending within the fixed peripheral portion of the wheel guard assembly 20.

The grinding wheel guard assembly described above is complemented by a distortion resisting and energy absorbing assembly generally designated by the reference numeral 60 including a rectangular side frame 61 of metal or other suitable material secured by attachment screws to the steel plate forming the closed upper plate of base 11, a cover plate 62 of metal or other suitable material, with dependent flanged edges to shed impinging coolant fluid, secured by attachment screws to the rectangular side frame 61, and within side frame 61 and beneath cover plate 62 alternate layers of a relatively rigid high strength material such as steel plates and individual or multiple sheets of a suitable compressive energy absorbing material, for example, the high energy absorbing material available commercially from Norton Company under the trademark E-A-R, or other suitable such material.

The number and thickness of the respective sheets of relatively rigid material and of energy absorbing material are selected to provide effective distribution of concentrated loads over wide areas of the energy absorbing material and effective energy absorbtion for the greatest load reasonably to be expected in a given installation, considering the function of the steel plates or other material resistant to local distortion is to transfer multiple concentrated loads to substantially the entire surface area of the energy absorbing material, to minimize the thickness of energy absorbing material required.

Alternatively, the space within the side frame 61 and beneath the cover plate 62 may be filled with a single block or several separate layers of any one or a combination of different suitable energy absorbing materials.

Thus the energy absorbing assembly described above, supported separately from and not movable with the grinding wheel guard assembly, but disposed closely adjacent and parallel to its open peripheral side below the grinding wheel, coacts with the lower rear portion of the grinding wheel guard assembly to confine the wheel fragments driven thereagainst, and also protects from damage the steel plate forming the upper surface of the base 11 and comprising an important structural element of a fabricated grinding machine base. In this manner, the energy absorbing assembly mounted upon the grinding machine, as shown in the accompanying drawing, is supported adjacent to and spans the open peripheral portion of the grinding wheel guard assembly.

In addition, a grinding wheel guard assembly as shown in FIG. 1 with a vertically extended lower peripheral portion at the rear may be used with a hollow cast iron base to further assure the deliveryof all wheel fragments into the receptacle formed by the hollow base, and the distortion resistin and energy absorbing assembly shown in FIG. 1 may be use In a similar manner with other suitable grinding wheel guard designs.

Finally, the small space between the lower end of the grinding wheel guard assembly and the cover plate of the distortion resisting and energy absorbing assembly permits the drainage of the substantial quantity of coolant fluid directed against the workpiece and the grinding wheel during each grinding operation and thence into the grinding wheel guard assembly, and also provides ready access for the periodic removal of the quantities of swarf collected on top of the cover plate of the distortion resisting and energy absorbing assembly.

It is to be understood that the preferred embodiment of the present invention described herein is intended to be illustrative and not limiting in any manner as the invention is limited only by the scope of the appended claims.

I claim:

1. For use on a grinding machine including a grinding wheel rotating about a predetermined axis of rotation,

a grinding wheel guard assembly mounted upon the grinding machine having a first portion that is closed and extends around a first portion of the periphery of the grinding wheel and a second portion that is open and extends around an adjacent second portion of the periphery of the grinding wheel, and

a laminar distortion resisting and energy absorbing device mounted upon the grinding machine adjacent to and spanning the second open portion of the grinding wheel guard, the energy absorbing device being subjected to a scattered multiplicity of concentrated high impact loads from the fragments of the grinding wheel in the event of failure of the grinding wheel,

said laminar distortion resisting and energy absorbing device comprising:

at least one overlying sheet of relatively rigid high strength material resistant to local deformation, and

at least one underlying layer of high energy absorbing material supported beneath and in engagement with each said sheet of relatively rigid high strength material,

whereby the force of each impact load upon a relatively smaller area of each said overlying sheet of relatively rigid high strength material is distributed through each said overlying sheet over a relatively larger area of each said underlying layer of high energy absorbing material.

2. A laminar distortion resisting and energy absorbing device as described in claim 1 comprising:

a predetermined plurality of generally planar alternate overlying sheets of relatively rigid high strength material, and

a predetermined plurality of generally planar alternate underlying layers of high energy absorbing material. 

1. For use on a grinding machine including a grinding wheel rotating about a predetermined axis of rotation, a grinding wheel guard assembly mounted upon the grinding machine having a first portion that is closed and extends around a first portion of the periphery of the grinding wheel and a second portion that is open and extends around an adjacent second portion of the periphery of the grinding wheel, and a laminar distortion resisting and energy absorbing device mounted upon the grinding machine adjacent to and spanning the second open portion of the grinding wheel guard, the energy absorbing device being subjected to a scattered multiplicity of concentrated high impact loads from the fragments of the grinding wheel in the event of failure of the grinding wheel, said laminar distortion resisting and energy absorbing device comprising: at least one overlying sheet of relatively rigid high strength material resistant to local deformation, and at least one underlying layer of high energy absorbing material supported beneath and in engagement with each said sheet of relatively rigid high strength material, whereby the force of each impact load upon a relatively smaller area of each said overlying sheet of relatively rigid high strength material is distributed through each said overlying sheet over a relatively larger area of each said underlying layer of high energy absorbing material.
 2. A laminar distortion resisting and energy absorbing device as described in claim 1 comprising: a predetermined plurality of generally planar alternate overlying sheets of relatively rigid high strength material, and a predetermined plurality of generally planar alternate underlying layers of high energy absorbing material. 